Semiconductor device and fabricating the same

ABSTRACT

The present disclosure provides a method for fabricating an integrated circuit device. The method includes providing a precursor including a substrate having first and second metal-oxide-semiconductor (MOS) regions. The first and second MOS regions include first and second gate regions, semiconductor layer stacks, and source/drain regions respectively. The method further includes laterally exposing and oxidizing the semiconductor layer stack in the first gate region to form first outer oxide layer and inner nanowire set, and exposing the first inner nanowire set. A first high-k/metal gate (HK/MG) stack wraps around the first inner nanowire set. The method further includes laterally exposing and oxidizing the semiconductor layer stack in the second gate region to form second outer oxide layer and inner nanowire set, and exposing the second inner nanowire set. A second HK/MG stack wraps around the second inner nanowire set.

PRIORITY DATA

The present application is a divisional application of U.S. patentapplication Ser. No. 13/957,500, filed Aug. 2, 2013, which isincorporated herein by reference in its entirety.

CROSS-REFERENCE

This application is related to U.S. Ser. No. 13/957,102 filed on Aug. 1,2013, which is hereby incorporated by reference.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experiencedexponential growth. Technological advances in IC materials and designhave produced generations of ICs where each generation has smaller andmore complex circuits than the previous generation. In the course of ICevolution, functional density (i.e., the number of interconnecteddevices per chip area) has generally increased while geometry size(i.e., the smallest component (or line) that can be created using afabrication process) has decreased. This scaling down process generallyprovides benefits by increasing production efficiency and loweringassociated costs.

Such scaling down has also increased the complexity of processing andmanufacturing ICs and, for these advances to be realized, similardevelopments in IC processing and manufacturing are needed. For example,a three dimensional transistor, has been introduced to replace a planartransistor. Although existing semiconductor devices and methods offabricating semiconductor devices have been generally adequate for theirintended purposes, they have not been entirely satisfactory in allrespects. For example, to introduce three dimensional nanostructure to agate channel raises challenges in a semiconductor device processdevelopment. It is desired to have improvements in this area.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIG. 1 is a flow chart of an example method for fabricating an N-typemetal-oxide-semiconductor (NMOS) region and a P-typemetal-oxide-semiconductor (PMOS) region in an integrated circuit (IC)device according to various aspects of the present disclosure.

FIG. 2A is a diagrammatic perspective view of a device precursoraccording to some embodiments of the present disclosure.

FIGS. 2B and 2C are cross-sectional views of the device precursor alongthe line A-A and line B-B in FIG. 2A respectively according to someembodiments of the present disclosure.

FIG. 3A is a diagrammatic perspective view of ametal-oxide-semiconductor (MOS) region in the IC device at anintermediate stage constructed according to the method of FIG. 1.

FIGS. 3B, and 4A-6A are cross-sectional views of the semiconductordevice along the line A-A in FIG. 3A at various fabrication stagesconstructed according to the method of FIG. 1.

FIGS. 3C, and 4B-6B are cross-sectional views of the semiconductordevice along the line B-B in FIG. 3A at various fabrication stagesconstructed according to the method of FIG. 1.

FIGS. 5C-6C are cross-sectional views of the semiconductor device alongthe line C-C in FIG. 3A at various fabrication stages constructedaccording to the method of FIG. 1.

FIGS. 7A-15A are cross-sectional views of the NMOS region and the PMOSregion of the IC device along the line A-A in FIG. 3A at variousfabrication stages constructed according to the method of FIG. 1.

FIGS. 7B-15B are cross-sectional views of the NMOS region and the PMOSregion of the IC device along the line B-B in FIG. 3A at variousfabrication stages constructed according to the method of FIG. 1.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. For example, if the device in the figures is turned over,elements described as being “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the exemplary term “below” can encompass both an orientation ofabove and below. The apparatus may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein may likewise be interpreted accordingly.

The present disclosure is directed to, but not otherwise limited to, acomplementary metal-oxide-semiconductor (CMOS) device comprising aP-type metal-oxide-semiconductor (PMOS) device and an N-typemetal-oxide-semiconductor (NMOS) device. The following disclosure willcontinue with a CMOS device example to illustrate various embodiments ofthe present invention. It is understood, however, that the presentdisclosure should not be limited to a particular type of device, exceptas specifically claimed. It is also understood that additional steps canbe provided before, during, and after the method, and some of the stepsdescribed can be replaced or eliminated for other embodiments of themethod.

Referring to FIGS. 1 and 2A-2C, the method 100 begins at step 102 byproviding a device precursor 150. Device precursor 150 may be aprecursor used to fabricate a metal-oxide-semiconductor (MOS) region,such as MOS region 200, 300 and/or 400 (as shown in FIGS. 3-15). Deviceprecursor 150 includes a substrate 210. Substrate 210 may include bulksilicon. Alternatively, an elementary semiconductor, such as silicon orgermanium in a crystalline structure, may also be included in substrate210. Device precursor 150 may also include a compound semiconductor,such as silicon germanium, silicon carbide, gallium arsenic, galliumphosphide, indium phosphide, indium arsenide, and/or indium antimonide;or combinations thereof. Possible substrates 210 also include asemiconductor-on-insulator substrate, such as silicon-on-insulator(SOI), SiGe-On-Insulator (SGOI), Ge-On-Insulator substrates. Forexample, the SOI substrates may be fabricated using separation byimplantation of oxygen (SIMOX), wafer bonding, and/or other suitablemethods.

Various doped regions may also be included in substrate 210 depending ondesign requirements. The doped regions may be doped with p-type dopants,such as boron or BF₂. The doped regions may also be doped with n-typedopants, such as phosphorus or arsenic. The doped regions may also bedoped with combinations of p-type and n-type dopants. The doped regionsmay be formed directly on substrate 210, in a P-well structure, in anN-well structure, in a dual-well structure, or using a raised structure.

An anti-punch through (APT) region 212 may be formed in the upperportion of substrate 210 and below semiconductor layer stack 230. APTregion 212 may be formed to prevent device punch-through issue andprovide better leakage control. In some examples, when the deviceprecursor 150 is used to fabricate an NMOS unit, APT region 212 insubstrate 210 may be doped with p-type dopants, such as boron and/orBF₂. In some examples, when the device precursor 150 is used tofabricate a PMOS unit, APT region 212 in substrate 210 may be doped withn-type dopants, such as phosphorus and/or arsenic.

Referring to FIGS. 2A-2C, device precursor 150 may also include one ormore isolation regions 220. Isolation regions 220 are formed oversubstrate 210 to isolate active regions. For example, each isolationregion 220 separates semiconductor layer stacks 230 from each other.Isolation regions 220 may be formed using traditional isolationtechnology, such as shallow trench isolation (STI), to define andelectrically isolate the semiconductor layer stacks. In some examples,isolation regions 220 may include silicon oxide, silicon nitride,silicon oxynitride, an air gap, other suitable materials, orcombinations thereof. Isolation regions 220 may be formed by anysuitable process. In some examples, the formation of an STI includes aphotolithography process, etching a trench in substrate 210 (forexample, by using a dry etching and/or wet etching), and filling thetrench (for example, by using a chemical vapor deposition process) withone or more dielectric materials to form isolation regions 220. In someexamples, the filled trench may have a multi-layer structure such as athermal oxide liner layer filled with silicon nitride or silicon oxide.In some embodiments, a chemical mechanical polishing (CMP) process isperformed to remove excessive dielectric materials and planarize the topsurface of the isolation regions.

As shown in FIG. 2A, the isolation region disposed at the side of thedevice precursor 150 is inter isolation region, and the isolation regiondisposed between the semiconductor layer stacks 230 is intra isolationregion. In some embodiments, the depth of the inter isolation region(D1) is greater than the depth of the intra isolation region (D2). Forexample as shown in FIG. 2A, D1 may be in the range of 60-120 nm. D2 maybe in the range of 40-60 nm.

Still referring to FIGS. 2A-2C, device precursor 150 includes one ormore semiconductor layer stacks 230 formed over substrate 210. Theformation process of semiconductor layer stacks 230 may includephotolithography and etching processes. The photolithography process mayinclude forming a photoresist layer (resist) overlying the substrate,exposing the resist to a pattern, performing a post-exposure bakeprocess, and developing the resist to form a masking element includingthe resist. The etching process may include any appropriate dry etchingand/or wet etching method. Semiconductor layer stacks 230 may beepitaxially grown after the recessing processes. In some embodiments,the thickness (T) of the recessed portions of substrate 210 may be inthe range of 30-50 nm. Alternatively, semiconductor layer stacks 230 maybe formed by patterning and etching a silicon layer deposited overlyingan insulator layer (for example, an upper silicon layer of asilicon-insulator-silicon stack of an SOI substrate.

As shown in FIGS. 2A-2C, semiconductor layer stacks 230 may includemultiple semiconductor layers. Each of the semiconductor layers may havesubstantial different thickness to each other. Semiconductor layerstacks 230 may include germanium (Ge), silicon (Si), gallium arsenide(GaAs), silicon germanium (SiGe), gallium arsenide phosphide (GaAsP), orother suitable materials. Semiconductor layer stacks 230 may bedeposited by epitaxial growing processes, such as chemical vapordeposition (CVD), Vapor Phase Epitaxy (VPE), ultra high vacuum(UHV)-CVD, molecular beam epitaxy (MBE), and/or other suitableprocesses. The surface of device precursor 150 including thesemiconductor layer stacks 230 may be then planarized using a CMPprocess.

Referring to FIG. 2B, semiconductor layer stacks 230 of device precursor150 may include one or more first layers 232 and one or more secondlayers 234 alternatingly stacked over each other. In some embodiments,the first layers 232 may include SiGe. The second layers 234 may includeSi. In some embodiments, semiconductor layer stacks 230 may include analternating structure as SiGe (232)/Si (234)/SiGe (232)/Si (234) frombottom to top. In some embodiments, the first layers 232 may have athickness in the range of 5-10 nm. The second layers 234 may have athickness in the range of 5-15 nm. In some embodiments, the thicknessesof the first layers 232 may be different from each other. Thethicknesses of the second layers 234 may be different from each other.In some embodiments, the percentage of Ge in the first layers SiGe 232may be in the range of 20-50%. In some embodiments, the concentration ofGe in the first layers SiGe 232 may be different in some layers fromothers.

Referring to FIGS. 2A and 2C, substrate 210 includes a source/drainregion 250 and a gate region 248. Source/drain regions 250 are separatedby gate region 248.

Referring to FIGS. 1 and 3A-3C, method 100 proceeds to step 104 byrecessing portions of isolation regions 220 to form recessing trenches240 to laterally expose semiconductor layer stacks 230. The recessingprocess may include a dry etching process, a wet etching process, and/orcombination thereof. The recessing process may include a selective wetetch or a selective dry etch. In some embodiments, the isolation regions220 may be recessed until the entire semiconductor layer stack 230 canbe exposed. It is noted that the following discussion will now refer todevice precursor 150 as a MOS region 200.

Referring to FIGS. 1 and 4A-4B, method 100 proceeds to step 105 byforming a dummy gate 242 and a hard mask 244 in gate region 248. Dummygate 242 and hard mask 244 may be formed over the semiconductor layerstacks 230 and isolation regions 220 in gate region 248. Dummy gate 242may include polysilicon. Dummy gate 242 may be formed by any suitableprocess or processes. For example, dummy gate 242 may be formed by aprocedure including depositing, photolithography patterning, and/oretching processes. The deposition processes include CVD, PVD, ALD, othersuitable methods, and/or combinations thereof. Hard mask 244 may includesilicon oxide, silicon nitride, silicon oxynitride, or any othersuitable dielectric material. Hard mask 244 may be a single layer ormultiple layers. Hard mask 244 may be formed by CVD, ALD, or any otherappropriate method.

Referring to FIGS. 1 and 4B, method 100 proceeds to step 106 by formingcommon source/drain recessing trenches 252 in MOS region 200. Referringto FIGS. 3A and 4B, portions of the semiconductor layer stack 230,isolation regions 220, and/or substrate 210 in the source/drain regions250 may be removed along the line C-C direction to form commonsource/drain trenches 252 in MOS region 200 using dummy gate 242 andhard mask 244. Common Source/drain recessing trenches 252 may be formedusing any kind of dry etching process, wet etching process, and/orappropriate combination thereof. The recessing process may also includea selective wet etch or a selective dry etch. The recessing process mayinclude multiple etching processes.

Still referring to FIG. 4B, sidewall spacers 246 may be formed alonggate region 248 after dummy gate 242 and hard mask 244 are formed.Sidewall spacers 246 may include a dielectric material such as siliconoxide, silicon nitride, silicon carbide, silicon oxynitride, orcombinations thereof. Sidewall spacers 246 may also include multiplelayers. Typical formation methods for the sidewall spacers includedepositing a dielectric material over gate region 248. The dielectricmaterial may be then anisotropically etched back. The etching backprocess may include a multiple-step etching to gain etch selectivity,flexibility and desired overetch control.

Referring to FIGS. 1 and 5A-5C, method 100 proceeds to step 108 byforming crown-shaped source/drain features 254 in common source/drainrecessing trenches 252. A semiconductor material epitaxially grows inthe common source/drain trenches 252 to form the crown-shapedsource/drain features 254. The semiconductor material includes Ge, Si,GaAs, AlGaAs, SiGe, GaAsP, or other suitable material. Crown-shapedsource/drain features 254 may be formed by one or more epitaxy orepitaxial (epi) processes. Crown-shaped source/drain features 254 may bein-situ doped during the epi process. For example, the epitaxially grownSiGe source/drain features 254 may be doped with boron; and theepitaxially grown Si epi source/drain features 254 may be doped withcarbon to form Si:C source/drain features, phosphorous to form Si:Psource/drain features, or both carbon and phosphorous to form SiCPsource/drain features. In some embodiments, an implantation process(i.e., a junction implant process) is performed to dope crown-shapedsource/drain features 254. One or more annealing processes may beperformed to activate source/drain epitaxial feature. In someembodiments, a crown-shaped source/drain feature is a crown-shapedsource region, and the other crown-shaped source/drain feature is acrown-shaped drain region. A crown-shaped source feature is separated bygate region 248 from a crown-shaped drain feature.

Although only common source/drain trenches 252 and crown-shapedsource/drain features 254 are illustrated in the present disclosure, thesource/drain trench 252 may be formed in an individual type separated byisolation regions 220, referred to as an individual source/draintrenches 252. Individual source/drain features 254 may be formed byepitaxially growing the semiconductor material in the individualsource/drain trenches 252.

Referring to FIGS. 1 and 6A-6C, method 100 proceeds to step 110 byforming an interlayer dielectric (ILD) layer 256 over crown-shapedsource/drain features 254. ILD layer 256 may include silicon oxide,oxynitride or other suitable materials. ILD layer 256 may include asingle layer or multiple layers. ILD layer 256 may be formed by asuitable technique, such as CVD, ALD and spin-on technique. Afterforming ILD layer 256, CMP processes may be performed to removeexcessive ILD layer 256 and planarize the top surface of ILD layer 256.In some embodiments, hard mask 244 may also be removed during the CMPprocesses as shown in FIGS. 6A-6C.

Referring to FIGS. 1 and 6A-6C, method 100 proceeds to step 112 byforming a patterned hard mask 258 to cover MOS region 200. Afterremoving excessive ILD layers 256 and planarizing the surface of MOSregion 200 at step 110, the surface of the MOS region 200 may be coveredwith a patterned hard mask 258 to prevent MOS region 200 from beingaffected during the processes carried out in other regionssimultaneously. Hard mask 258 may include silicon oxide, siliconnitride, silicon oxynitride, or any other suitable dielectric material.Hard mask 258 may include a single layer or multiple layers. Hard mask258 may be formed by CVD, ALD, or any other appropriate method.

Referring to FIGS. 7-15, more than one MOS region 200 may be used toform different types of MOS regions in an IC device 500 simultaneouslyor separately. In some examples as illustrated in the presentdisclosure, an NMOS region 300 and PMOS region 400 may be formed in ICdevice 500 using method 100 as shown in FIG. 1. Alternatively, MOSregion 300 may be a PMOS region 300, and MOS region 400 may be an NMOSregion 400.

Referring to FIGS. 1 and 7A-7B, method 100 proceeds to step 113 byremoving dummy gate 242 to expose semiconductor layer stacks 230 in gateregion 248. In PMOS regions 400, gate region 248 is referred to as gateregion 448. Dummy gate 242 of PMOS region 400 may be removed to expose agate stack 449 as shown in FIG. 7B. Gate stack 449 may includesemiconductor layer stack 230 disposed in gate region 448. Dummy gate242 may be removed using any appropriate method, such as etchingprocesses. The etching processes may include selective wet etch orselective dry etch, such that dummy gate 242 has an adequate etchselectivity with respect to gate stack 449, and the sidewall spacers246. Alternatively, dummy gate 242 may be recessed by a series ofprocesses including photolithography patterning and etching back.

Referring to FIGS. 1 and 8A-8B, method 100 proceeds to step 114 byoxidizing portions of the gate stack 449 in gate region 448 of PMOSregion 400 to form an outer oxide layer 436 and an inner nanowire 438.In some embodiments, a thermal oxidation process may be performed on thefirst layers 232 and the second layers 234 of gate stack 449. In someexamples, the thermal oxidation process is conducted in oxygen ambient.In some examples, the thermal oxidation process may be conducted in acombination of steam ambient and oxygen ambient. The thermal oxidationprocess may be conducted in a combination of steam ambient and oxygenambient with one atmospheric pressure and a temperature in a range from400° C. to 600° C. The thermal oxidation process may be conducted for30-180 minutes.

During the thermal oxidation process, an element of the first layers 232and the second layers 234 are oxidized to form an outer oxide layer 436.In some embodiments, outer oxide layer 436 may include silicon oxide(SiOx), where x is oxygen composition in atomic percent. In someembodiments, another element of the first layers 232 may diffuse to theinside of outer oxide layer 436 to form a semiconductor core portion 438during the oxidation process. Semiconductor core portion 438 may beformed continuously along the line B-B direction (as shown in FIG. 3A),and connected to the crown-shaped source/drain features 254 on bothsides of gate region 448. It is noted that the following discussion willnow refer to semiconductor core portion 438 as an inner semiconductornanowire 438. In some embodiments, the inner semiconductor nanowire 438may be Ge nanowire 438. The outer oxide layer 436 may be formed to wrapthe inner semiconductor nanowire 438. In some embodiments, more than oneinner semiconductor nanowire 438 may be formed in a nanowire set 439 inouter oxide layer 436.

Referring to FIGS. 8A-8B, in some examples, the diameter of the innersemiconductor nanowire 438 may be in the range of 2-15 nm. The size andshape of outer oxide layer 436 and/or inner semiconductor nanowire 438may vary with different process conditions, such as thermal oxidationtemperature and time.

Referring to FIGS. 1 and 9A-9B, method 100 proceeds to step 116 byremoving outer oxide layer 436 to expose one or more inner semiconductornanowires 438 in PMOS region 400. The removing process may include a dryetch, a wet etch, or a combination of. For example, a selective wet etchor a selective dry etch of outer oxide layer 436 is performed withadequate etch selectivity with respect to inner semiconductor nanowire438. After removing outer oxide layer 436, gate region 448 of the PMOSregion 400 is configured to include one or more inner semiconductornanowires 438 formed in nanowire set 439.

Referring to FIGS. 1 and 10A-10B, method 100 proceeds to step 118 byforming interfacial layer (IL) 462/high-k (HK) dielectric layer464/metal gate (MG) 466 in PMOS region 400. In some embodiments, one ormore ILs 462 may be formed to wrap around one or more inner nanowires438, and cover sidewall spacers 246. IL 462 may be deposited by anyappropriate method, such as ALD, chemical vapor deposition CVD and ozoneoxidation. IL 462 may include oxide, HfSiO and oxynitride. In someembodiments, the interface between the isolation region 220 and the IL462 may not be observed after the thermal treatment. One or more HKdielectric layers 464 may be deposited over and wrapping around ILs 462by any suitable techniques, such as ALD, CVD, metal-organic CVD (MOCVD),physical vapor deposition (PVD), thermal oxidation, combinationsthereof, or other suitable techniques. HK dielectric layer 464 mayinclude LaO, AlO, ZrO, TiO, Ta₂O₅, Y₂O₃, SrTiO₃ (STO), BaTiO₃ (BTO),BaZrO, HfZrO, HfLaO, HfSiO, LaSiO, AlSiO, HfTaO, HfTiO, (Ba,Sr)TiO₃(BST), Al₂O₃, Si₃N₄, oxynitrides (SiON), or other suitable materials. IL462 may include oxide, HfSiO and oxynitride. In some embodiments, theinterface between the IL 462 and the HK dielectric layer 464 may not beobserved after the thermal treatment.

An MG layer 466 may include a single layer or multi layers, such asmetal layer, liner layer, wetting layer, and adhesion layer. MG layer466 may include Ti, Ag, Al, TiAlN, TaC, TaCN, TaSiN, Mn, Zr, TiN, TaN,Ru, Mo, Al, WN, Cu, W, or any suitable materials. MG layer 466 may beformed by ALD, PVD, CVD, or other suitable process. A CMP process may beperformed to remove excessive MG layer 466. The CMP process provides asubstantially planar top surface for gate region 448 as well as ILDlayers 256 in PMOS region 400. After depositing IL 462/HK layer 464/MG466, gate region 448 may include one or more semiconductor nanowires438, and IL 462/HK layer 464/MG 466 as shown in FIG. 10B.

Referring to FIGS. 10A-10B, in some embodiments at step 118, hard mask258 over NMOS region 300 may be removed during the planarization of thesurface of PMOS region 400 using a CMP process.

Referring to FIGS. 1 and 11A-11B, method 100 proceeds to step 120 byforming a hard mask 468 over PMOS region 400 to prevent PMOS region 400from being affected during the following processes of NMOS region 300.Hard mask 468 may include silicon oxide, silicon nitride, siliconoxynitride, or any other suitable dielectric material. Hard mask 468 mayinclude a single layer or multiple layers. Hard mask 468 may be formedby CVD, PVD, ALD, or any other appropriate method.

Still referring to FIGS. 11A-11B, in some embodiments at step 120, dummygate 242 may be removed to expose gate stack 349 in gate region 348 ofNMOS region 300. Gate stack 349 may include semiconductor layer stack230 disposed in gate region 348 of NMOS region 300. Dummy gate 242 maybe removed using any appropriate method, such as etching processes. Theetching processes may include selective wet etch or selective dry etch,such that dummy gate 242 has an adequate etch selectivity with respectto gate stack 349, and the sidewall spacers 246. Alternatively, dummygate 242 may be recessed by a series of processes includingphotolithography patterning and etching back.

Referring to FIGS. 1 and 12A-12B, method 100 proceeds to step 122 byselectively removing the first layers 232 of NMOS region 300. In someembodiments, the first layers 232 may include SiGe, and the SiGe may beremoved using any appropriate etching process, such as dry etchingprocess, wet etching process, and/or combination thereof. The removingprocess of the first layers 232 may also include a selective wet etch ora selective dry etch, such that it offers adequate etch selectivity withrespect to the second layers 234. In some examples, the selective wetetch or the selective dry etch may selectively remove the entire firstlayers 232. The dry and wet etching processes may have etchingparameters that can be tuned, such as etchants used, etchingtemperature, etching solution concentration, etching pressure, sourcepower, RF bias voltage, RF bias power, etchant flow rate, and othersuitable parameters. Dry etching processes may include a biased plasmaetching process that uses a chlorine-based chemistry. Other dry etchantgasses may include Tetrafluoromethane (CF₄), Chlorine trifluoride(ClF₃). Dry etching may also be performed anisotropically using suchmechanisms as DRIE (deep reactive-ion etching). Chemical vapor etchingmay be used as a selective etching method, and the etchant gaseous mayinclude hydrogen chloride (HCl), Tetrafluoromethane (CF₄), and gasmixture with hydrogen (H₂). Chemical vapor etching may be performed byChemical Vapor Deposition (CVD) with suitable pressure and temperature.

Referring to FIGS. 1 and 13A-13B, method 100 proceeds to step 124 byoxidizing the second layers 234 in gate region 348 of NMOS region 300 toform an outer oxide layer 336 and an inner semiconductor nanowire 338.In some examples, the thermal oxidation process is conducted in oxygenambient. In some examples, the thermal oxidation process may beconducted in a combination of steam ambient and oxygen ambient. Thethermal oxidation process may be conducted in a combination of steamambient and oxygen ambient with one atmospheric pressure and atemperature in a range from 400° C. to 600° C. The thermal oxidationprocess may be conducted for 30-180 minutes.

During the thermal oxidation process, an outer portion of the secondlayer 234 may be oxidized to form an outer oxide layer 336. In someembodiments, outer semiconductor oxide layer 336 may include siliconoxide (SiOx), where x is oxygen composition in atomic percent. In someembodiments, an inner portion of the second layer 234 may diffuse to theinside of outer oxide layer 336 to form a semiconductor core 338 duringthe oxidation process. Semiconductor core portion 338 may becontinuously along the line B-B direction (as shown in FIG. 2A), andconnected to the crown-shaped source/drain features 254 on both sides ofgate region 348. It is noted that the following discussion will nowrefer to semiconductor core portion 338 as an inner semiconductornanowire 338. In some embodiments, the inner semiconductor nanowire 338may be Si nanowire 338. The outer oxide layer 336 may be formed to wrapthe inner semiconductor nanowire 338. In some embodiments, more than oneinner semiconductor nanowire 338 may be formed in a nanowire set 339 inouter oxide layer 336.

Referring to FIGS. 13A-13B, in some examples, the diameter of innersemiconductor nanowire 338 may be in the range of 2-13 nm. The size andshape of the outer semiconductor oxide layer 336 and/or the innersemiconductor nanowire 338 may vary with different process conditions,such as thermal oxidation temperature and time.

Referring to FIGS. 1 and 14A-14B, method 100 proceeds to step 126 byremoving the outer oxide layer 336 to expose one or more innersemiconductor nanowires 338 in NMOS region 300. The removing process mayinclude a dry etch, a wet etch, or a combination of. For example, aselective wet etch or a selective dry etch of outer oxide layer 336 isperformed with adequate etch selectivity with respect to innersemiconductor nanowire 338. After removing the outer oxide layer 336,gate region 348 of NMOS 300 is configured to include one or more innersemiconductor nanowires 338 in nanowire set 339.

Referring to FIGS. 1 and 15A-15B, method 100 proceeds to step 128 byforming interfacial layer (IL) 362/high-k (HK) layer 364/metal gate (MG)366 in NMOS region 300. One or more ILs 362 may be formed to wrap aroundone or more inner nanowires 338, and cover sidewall spacers 246. One ormore HK dielectric layers 364 may be deposited over and wrapping aroundILs 362. The formation processes and materials used to form IL 362, HKdielectric layer 364 and MG layer 366 may be substantially similar tothe formation processes and materials used to form IL 462, HK dielectriclayer 464 and MG layer 466, as described in FIGS. 10A-10B. In someembodiments, the interface between the IL 362 and the isolation region220 may not be observed after the thermal treatment. The interfacebetween the IL 362 and the HK dielectric layer 364 may not be observedafter the thermal treatment. After depositing IL 362/HK layer 364/MG366, gate region 348 may include one or more inner semiconductornanowires 338, and IL 362/HK layer 364/MG 366.

Still referring to FIGS. 1 and 15A-15B, at step 128, hard mask 468covering PMOS region 400 may be removed. In some embodiments, hard mask468 may be removed during the planarization of the surface of NMOSregion 300 using a CMP process.

Although according to the illustrations in FIGS. 7-15, the nanowirestructure in PMOS region 400 are formed prior to the formation of thenanowire structure in NMOS region 300, the nanowire structure in NMOSregion 300 may be formed prior to the formation of the nanowirestructure in PMOS region 400. In some embodiments, a hard mask may befirst formed to cover PMOS region 400 during the formation of thenanowire in NMOS region 300. In some embodiments, the nanowire structuremay be only formed in NMOS region 300. In some embodiments, the nanowirestructure may be only formed in PMOS region 400. In some embodiments,there is more than one nanowire formed in NMOS region 300 and/or PMOSregion 400. A person having ordinary skill in the art would be able tounderstand that NMOS region 300 and PMOS region 400 may be formed usingany suitable processes in any appropriate order and in any propertopology.

In some embodiments, MG layer 366 of NMOS region 300 may also include afirst capping layer wrapping around IL 362/HK layer 364 structure. Afirst barrier MG and n-type work function (NWF) MG may be further formedto wrap around the first capping layer. MG layer 466 of PMOS region 400may also include a second capping layer wrapping around IL462/HK layer464 structure. A second barrier MG and p-type work function (PWF) MG maybe further formed to wrap around the second capping layer. The firstand/or second capping layer may include TiN. The first and/or secondbarrier MG may include TaN. The NWF MG of NMOS region 200 may be formedusing different metal layers from the PWF MG layer of PMOS region 300.In some examples, the NWF MG may include TiAlC, TaAl, and/or TiAl. ThePWF MG may include TiN.

NMOS region 300 and/or PMOS region 400 of IC device 500 may undergofurther CMOS or MOS technology processing to form various features andregions known in the art. For example, subsequent processing may formvarious contacts/vias/lines and multilayers interconnect features (e.g.,metal layers and interlayer dielectrics) on substrate 210, configured toconnect the various features or structures of IC device 500. Forexample, a multilayer interconnection includes vertical interconnects,such as conventional vias or contacts, and horizontal interconnects,such as metal lines. The various interconnection features may implementvarious conductive materials including copper, tungsten, and/orsilicide. In one example, a damascene and/or dual damascene process isused to form a copper related multilayer interconnection structure.

Additional steps can be provided before, during, and after method 100,and some of the steps described can be replaced or eliminated for otherembodiments of the method.

The present disclosure provides many different embodiments of a methodfor fabricating an integrated circuit (IC) device. The method includesproviding a precursor. The precursor includes a substrate having firstand second metal-oxide-semiconductor (MOS) regions; first gate andsource/drain regions formed in the first MOS region, the first gateregion including a semiconductor layer stack; and second gate andsource/drain regions formed in the second MOS region, the second gateregion including the semiconductor layer stack. The semiconductor layerstack includes one or more first layers and one or more second layersalternatingly disposed over the substrate. The method further includeslaterally exposing the semiconductor layer stack in the first gateregion; oxidizing the semiconductor layer stack in the first gate regionto form first outer oxide layer and inner nanowire set, a first nanowirein the first inner nanowire set extending from the first source regionto the corresponding first drain region; removing the first outer oxidelayer to expose the first inner nanowire set in the first gate region;forming a first high-k/metal gate (HK/MG) stack wrapping around thefirst inner nanowire set; laterally exposing the semiconductor layerstack in the second gate region; oxidizing the semiconductor layer stackin the second gate region to form second outer oxide layer and innernanowire set, a second nanowire in the second inner nanowire setextending from the second source region to the second drain region;removing the second outer oxide layer to expose the second innernanowire set in the second gate region; and forming a second HK/MG stackwrapping around the second inner nanowire set.

In another embodiment, an IC device includes a substrate having anN-type metal-oxide-semiconductor (NMOS) region and a P-typemetal-oxide-semiconductor (PMOS) region; a first gate region, and afirst source feature separated from a corresponding first drain featureby the first gate region in the NMOS region; and a second gate region,and a second source feature separated from a corresponding second drainfeature by the second gate region in the PMOS region. The first gateregion includes a plurality of first nanowire sets having a firstsemiconductor material. The first nanowire sets extend from the firstsource feature to the corresponding first drain feature. The second gateregion includes a plurality of second nanowire sets having a secondsemiconductor material. The second nanowire sets extend from the secondsource feature to the corresponding second drain feature. Each of theNMOS region and PMOS region includes at least one intra-isolation regionbetween nanowire sets, and at least one inter-isolation region at oneside of each of the NMOS region and PMOS region. A depth of theinter-isolation region is greater than a depth of the intra-isolationregion

In yet another embodiment, an IC device includes a substrate including ametal-oxide-semiconductor (MOS) region; a gate region disposed over thesubstrate; and a source separated from a corresponding drain feature bythe gate region. The gate region includes a plurality of nanowire setsextending from the source feature to the corresponding drain feature.The nanowire sets include a semiconductor material selected from a groupconsisting of Si and SiGe. The MOS region includes at least oneintra-isolation region between the nanowire sets, and at least oneinter-isolation region at one side of the MOS region. A depth of theinter-isolation region is greater than a depth of the intra-isolationregion

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. An integrated circuit device comprising: asubstrate having an N-type metal-oxide-semiconductor (NMOS) region and aP-type metal-oxide-semiconductor (PMOS) region; a first gate region anda first source feature separated from a corresponding first drainfeature by the first gate region in the NMOS region; and a second gateregion and a second source feature separated from a corresponding seconddrain feature by the second gate region in the PMOS region, wherein thefirst gate region includes a plurality of first nanowire sets having afirst semiconductor material, the first nanowire sets extending from thefirst source feature to the corresponding first drain feature, whereinthe second gate region includes a plurality of second nanowire setshaving a second semiconductor material, the second nanowire setsextending from the second source feature to the corresponding seconddrain feature, wherein each of the NMOS region and PMOS region includesat least one intra-isolation region between nanowire sets and at leastone inter-isolation region at one side of each of the NMOS region andPMOS region, wherein a depth of the inter-isolation region is greaterthan a depth of the intra-isolation region, and wherein an anti-punchthrough feature is disposed in the substrate under one of the firstnanowire sets from the plurality of first nanowire sets and a sidewallspacer extends along a sidewall of the anti-punch through feature. 2.The device of claim 1, wherein the first semiconductor material includesSi.
 3. The device of claim 1, wherein the second semiconductor materialincludes SiGe.
 4. The device of claim 1, further comprising: a firstanti-punch through (APT) region formed below the first nanowire sets,the first APT implanted with p-type dopants; and a second APT regionformed below the second nanowire sets, the second APT implanted withn-type dopants.
 5. The device of claim 1, wherein the depth of theintra-isolation is in the range of about 40 nm to about 60 nm.
 6. Thedevice of claim 1, wherein the depth of the inter-isolation is in therange of about 60 nm to about 120 nm.
 7. A device comprising: a firstnanowire extending from a first source/drain feature to a secondsource/drain feature; a first gate dielectric layer wrapping around thefirst nanowire; a second nanowire extending from the first source/drainfeature to the second source/drain feature; a second gate dielectriclayer wrapping around the second nanowire; a metal gate electrodewrapping around the first and second gate dielectric layers andextending from the first gate dielectric layer to the second gatedielectric layer; a first dielectric isolation feature disposed in asubstrate between the first and second nanowires and extending to afirst depth within the substrate; a second dielectric isolation featuredisposed in the substrate adjacent the first nanowire and extending to asecond depth within the substrate, the second depth being different thanthe first depth; a first anti-punch through feature disposed in thesubstrate directly under the first nanowire, wherein the firstanti-punch through feature extends continuously from the firstdielectric isolation feature to the second dielectric isolation feature,and a sidewall spacer extending along a sidewall of the first anti-punchthrough feature.
 8. The device of claim 7, wherein the first nanowire isformed of Si.
 9. The device of claim 7 wherein the first nanowire isformed of Ge.
 10. The device of claim 7, further comprising: a thirddielectric isolation feature disposed in the substrate adjacent thesecond nanowire and extending to the second depth within the substrate;and a second anti-punch through feature disposed in the substratedirectly under the second nanowire, wherein the second anti-punchthrough feature extends continuously from the third dielectric isolationfeature to the first dielectric isolation feature.
 11. The device ofclaim 7, further comprising an interlayer dielectric layer disposed overthe first source/drain feature and having a top surface facing away fromthe substrate, and wherein a top surface of the metal gate electrode issubstantially coplanar with the top surface of the interlayer dielectriclayer.
 12. The device of claim 7, wherein the first nanowire physicallycontacts the sidewall spacer.
 13. The device of claim 7, furthercomprising a second anti-punch through feature disposed in the substratedirectly under the second nanowire; and another sidewall spacerextending along a sidewall of the second anti-punch through feature. 14.The device of claim 7, wherein the first nanowire is formed of adifferent material than the second nanowire.
 15. A device comprising: afirst nanowire extending from a first source/drain feature to a secondsource/drain feature, wherein the first nanowire is formed of a firstmaterial that includes germanium; a first gate dielectric layer wrappingaround the first nanowire; a second nanowire extending from a thirdsource/drain feature to a fourth source/drain feature, wherein thesecond nanowire is formed of a second material that includes silicon,the second material being different than the first material; a secondgate dielectric layer wrapping around the second nanowire; a first metalgate electrode wrapping around the first dielectric layer; a secondmetal gate electrode wrapping around the second dielectric layer; afirst dielectric isolation feature disposed in a substrate between thefirst and second nanowires and extending to a first depth within thesubstrate; a second dielectric isolation feature disposed in thesubstrate adjacent one of the first and second nanowires and extendingto a second depth within the substrate, the second depth being differentthan the first depth; a first anti-punch through feature disposed in thesubstrate directly under the first nanowire, wherein the firstanti-punch through feature extends continuously from the firstdielectric isolation feature to the second dielectric isolation feature;and a sidewall spacer extending along a sidewall of the first anti-punchthrough feature.
 16. The device of claim 15, further comprising: a thirdnanowire extending from the first source/drain feature to the secondsource/drain feature, wherein the third nanowire is formed of the firstmaterial that includes germanium; and a third gate dielectric layerwrapping around the third nanowire, and wherein the first metal gateelectrode wraps around the third gate dielectric layer and extendscontinuously from the first gate dielectric layer to the third gatedielectric layer.
 17. The device of claim 15, further comprising: athird nanowire extending from the third source/drain feature to thefourth source/drain feature, wherein the third nanowire is formed of thesecond material that includes silicon; and a third gate dielectric layerwrapping around the third nanowire, and wherein the second metal gateelectrode wraps around the third gate dielectric layer and extendscontinuously from the second gate dielectric layer to the third gatedielectric layer.
 18. The device of claim 15, further comprising a thirddielectric isolation feature disposed in the substrate adjacent thefirst nanowire and extending to the first depth within the substrate.19. The device of claim 18, further comprising an interlayer dielectriclayer disposed over the first source/drain feature, and wherein a topsurface of the first metal gate electrode is not covered by theinterlayer dielectric layer.
 20. The device of claim 18, furthercomprising a second anti-punch through feature disposed in the substratedirectly under the second nanowire; and another sidewall spacerextending along a sidewall of the second anti-punch through feature.